Unmanned aerial vehicle-mounted passive radar single-station positioning method based on Doppler frequency

Abstract

The invention discloses an unmanned aerial vehicle-mounted passive radar single-station positioning method based on Doppler frequency, and particularly relates to the technical field of radiation detection, and the method comprises the steps: passively receiving a signal of a target radiation source in a flight process of an unmanned aerial vehicle along a predetermined trajectory, and measuring the Doppler frequency change; respectively determining and recording a maximum Doppler frequency point and a minimum Doppler frequency point; calculating corresponding tangent slopes according to the position coordinates of the maximum Doppler frequency point and the minimum Doppler frequency point; determining two possible positions of the radiation source through a simultaneous tangent equation; the final position of the radiation source is the midpoint of the two possible positions. According to the unmanned aerial vehicle-mounted passive radar single-station positioning method based on the Doppler frequency, Doppler frequency change data in different directions are collected, and the positioning accuracy is improved; the maximum value and the minimum value of the Doppler frequency of different track parts are calculated, and the position of the radiation source is estimated by using the tangent slope of the Doppler frequency extreme point, so that the calculation process is simplified, and the calculation complexity is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of passive positioning, and particularly to a single-station positioning method for an airborne passive radar based on Doppler frequency for unmanned aerial vehicles. Background Art

[0002] Traditional active positioning devices achieve the positioning and tracking of targets by actively radiating electromagnetic waves and receiving the signals reflected by the targets. However, such devices are prone to exposing their own positions and facing risks such as electronic interference and electronic kill, and no longer meet the needs of modern information warfare. In contrast, passive positioning devices do not require active radiation of electromagnetic signals, but achieve positioning by passively receiving the signals of target radiation sources, and have good concealment and anti-interference capabilities, so they have become an important part of modern integrated combat systems.

[0003] Passive positioning can be divided into two categories: single-station and multi-station. Distributed multi-station passive positioning requires high synchronization between observation stations, but in practical applications, it faces problems such as unstable communication and difficult signal matching, so its applicability is limited. In contrast, single-station passive positioning only relies on a single observation platform to receive the signals of target radiation sources and calculates the target position through algorithms, and has the advantages of strong adaptability and high flexibility, so it has attracted much attention.

[0004] Airborne single-station passive positioning devices have strong maneuverability and have strong adaptability and survivability in complex environments, so they have become the most widely used form in passive positioning technology and have important research significance.

[0005] Currently, single-station passive positioning methods mainly include direction-finding positioning method, time-of-arrival positioning method, azimuth / time-of-arrival positioning method, Doppler frequency positioning method, azimuth / Doppler frequency positioning method, rate-of-change-of-phase-difference positioning method, Doppler frequency rate-of-change positioning method, etc. These methods have their own advantages and applicability in different scenarios, providing diverse technical means for achieving precise positioning and tracking of targets.

[0006] Among them, the Doppler frequency positioning method is a method that uses the Doppler frequency change caused by the movement of the target relative to the receiver to achieve target positioning. When the target moves relative to the receiver at a certain speed, the frequency of its radiation signal will undergo Doppler frequency shift, that is, the frequency will shift relative to when the target is stationary. By measuring this Doppler frequency shift, the relative speed between the target and the receiver can be inferred, and then the target positioning can be achieved. Summary of the Invention

[0007] The main object of the present invention is to provide a single-station positioning method for an airborne passive radar based on Doppler frequency, which can effectively solve the problem that traditional devices are prone to exposing their own positions and facing risks such as electronic interference and electronic kill, and no longer meet the needs of modern information warfare.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A Doppler frequency-based single-station positioning method for passive radar onboard an unmanned aerial vehicle comprises the following steps:

[0010] S1: The UAV flies along a predetermined figure-8 trajectory, which includes an upper circle and a lower circle, and the radius of each circle is R;

[0011] S2: During the flight, the drone passively receives the signal from the target radiation source and measures the Doppler frequency change;

[0012] S3: The maximum and minimum Doppler frequency points are determined in the flight trajectories of the UAV in the upper circle and the lower circle, respectively;

[0013] S4: Use the navigation and positioning tool of the drone to record the position coordinates of the maximum and minimum Doppler frequency points;

[0014] S5: Calculate the corresponding tangent slope according to the position coordinates of the maximum and minimum Doppler frequency points;

[0015] S6: Determine the two possible positions of the radiation source by solving the simultaneous tangent equations;

[0016] S7: The final position of the radiation source is the midpoint of the above two possible positions.

[0017] Preferably, the UAV measures and records the frequency points corresponding to the maximum and minimum values ​​of the radiation source signal in the flight trajectories of the upper circle and the lower circle, respectively, and the frequency points are respectively set to

[0018] Preferably, the navigation and positioning tools of the UAV include but are not limited to GPS, an inertial navigation system or a radio navigation system.

[0019] Preferably, the UAV flies for a time of

[0020] Preferably, the UAV calculates the corresponding radial velocities respectively during the flight of the upper circle and the lower circle of the "8"-shaped trajectory;

[0021] For the upper circle, the radial velocity is calculated as V r =v1*-cos(β-θ), where V1 represents the linear velocity of the drone, V r It represents the component of the linear velocity between the radiation source and the line connecting the point. The center angle of the UAV is θ, and the direction angle between the UAV and the radiation source is β.

[0022] For the lower circle, the radial velocity is calculated as V r =v1*-cos(β+θ), where V l Represents the linear velocity of the drone, V r It represents the component of the linear velocity between the radiation source and the line connecting the point. The center angle of the UAV is θ, and the direction angle between the UAV and the radiation source is β.

[0023] Preferably, the drone uses the measured Doppler frequency change to calculate the relative speed between the target and the drone through an algorithm, wherein the calculation formula of the Doppler frequency is: where f s is the signal source frequency, and c is the speed of light.

[0024] Preferably, after determining the maximum and minimum Doppler frequency points, the drone determines the position of the radiation source by calculating the tangent slope, wherein the calculation formula for the tangent slope of the upper tangent circle is: where κ 11 and κ 12 The upper circles represent the slopes of the tangents of the maximum Doppler frequency point and the minimum Doppler frequency point, respectively. The tangent equations of the upper circles passing through the maximum and minimum Doppler frequency points are:

[0025] Preferably, the calculation formula of the slope of the tangent line of the lower circle is: where κ 21 and κ 22 They represent the slopes of the tangents of the maximum Doppler frequency point and the minimum Doppler frequency point of the lower circle respectively. The tangent equation of the upper circle passing through the maximum and minimum Doppler frequency points is:

[0026] Preferably, the midpoint of the two positions of the drone in the upper circle and the lower circle of the "8"-shaped trajectory determined by the simultaneous tangent equations is used as the final position of the radiation source, where the position calculation formula is: Where (x1+x2) and (y1+y2) represent the position coordinates of the upper circle and the lower circle respectively.

[0027] Preferably, the position coordinates determined by the upper circle and the lower circle are confirmed by the formula:

[0028] The formula for calculating the coordinates of the upper circle position is:

[0029] The calculation formula for the position coordinates of the lower circle is:

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention utilizes a drone to fly along an "8"-shaped trajectory, collect Doppler frequency change data in different directions, and improve the accuracy of positioning; calculates the maximum and minimum Doppler frequencies of two different trajectory parts (the upper circle and the lower circle), and estimates the position of the radiation source using the tangent slope of the Doppler frequency extreme points, simplifying the calculation process and reducing the computational complexity.

[0032] 2. The method of the present invention does not require active radiation of electromagnetic signals, so it has good concealment and anti-interference capabilities, is applicable to modern integrated combat systems, and is applicable not only to drones but also to various mobile platforms such as satellites and vehicle-mounted systems, with wide applicability.

[0033] 3. The present invention utilizes the strong maneuverability of the drone, which has strong adaptability and survivability in complex environments, enabling the method of the present invention to effectively perform radiation source positioning in various environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the system positioning schematic diagram of the present invention;

[0035] Figure 2 is the schematic diagram of the radial velocity of the upper circle of the present invention;

[0036] Figure 3 is the schematic diagram of the radial velocity of the lower circle of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] To make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0038] As shown in Figure 1 、 Figure 2 and Figure 3 , a method for single-station positioning of an unmanned aerial vehicle (UAV)-borne passive radar based on Doppler frequency includes the following steps:

[0039] S1: The UAV flies along a predetermined "8"-shaped trajectory, which includes an upper circle and a lower circle, and the radius of each circle is R;

[0040] S2: During the flight, the UAV passively receives the signals of the target radiation source and measures the Doppler frequency change;

[0041] S3: In the flight trajectories of the upper circle and the lower circle of the UAV, respectively determine the maximum and minimum Doppler frequency points;

[0042] S4: Use the navigation and positioning tools carried by the UAV to record the position coordinates of the maximum and minimum Doppler frequency points;

[0043] S5: Calculate the corresponding tangent slopes based on the position coordinates of the maximum and minimum Doppler frequency points;

[0044] S6: Determine two possible positions of the radiation source by simultaneously solving the tangent equations;

[0045] S7: The final position of the radiation source is the midpoint of the above two possible positions.

[0046] Search, detect, and determine the parameters of the radiation source signal using radio - electronic means. The unmanned aerial vehicle (UAV) flies along an "8" - shaped trajectory relative to the Earth's surface, processes and transmits data during flight. The measured values are the spatial parameters of the UAV flight trajectory, determine the coordinate position of the UAV. The UAV conducts frequency search for the radiation source signal, finds the maximum and minimum Doppler frequencies in the flight trajectory. Due to the special "8" - shaped motion trajectory, there are two pairs of maximum and minimum Doppler frequencies (i.e., two maximum Doppler frequencies and two minimum Doppler frequencies), determine the positions of the four points, and make the corresponding tangents. Among them, the tangent corresponding to the upper circle determines one coordinate position, and the tangent corresponding to the lower circle determines one coordinate position. The midpoint of the two positions is taken as the position of the radiation source.

[0047] Specifically, the radio - navigation positioning tool determines the coordinates of the UAV, and the on - board search tool detects and evaluates the parameters of the target radiation source signal, searches for the radiation source signal within a given frequency range, and measures its frequency when the radiation source signal is detected.

[0048] Extra record the UAV motion positions corresponding to the maximum and minimum values of the radiation source signal frequency, draw the corresponding tangents in combination with the motion trajectory, and the intersection point of the tangent positions is the position of the target radiation source.

[0049] The intersection point coordinates of the pair of maximum and minimum Doppler frequency tangents corresponding to the upper circle of the "8" - shaped motion trajectory is position 1, and the intersection point coordinates of the pair of maximum and minimum Doppler frequency tangents corresponding to the lower circle is position 2. However, due to the existence of measurement errors, there may be deviations between position 1 and position 2. Therefore, the final determined position of the target radiation source is the midpoint of position 1 and position 2;

[0050] In Figure 1 The punctuation marks are as follows: 1. Manned aircraft; 2. Flight path of the UAV; 3. Maximum and minimum Doppler frequency position points of the UAV flight path; 4. Tangents of the UAV at the maximum and minimum frequency positions.

[0051] Furthermore, in the flight trajectories of the UAV in the upper circle and the lower circle, measure and record the frequency points corresponding to the maximum and minimum values of the radiation source signal respectively. The frequency points are respectively set as

[0052] Further, the navigation and positioning tools of the drone include, but are not limited to, GPS, inertial navigation systems, or radio navigation systems.

[0053] Further, the time for the drone to fly on each circle of the figure-eight trajectory is

[0054] Further, during the flight of the drone on the upper and lower circles of the figure-eight trajectory, the corresponding radial velocities are calculated respectively;

[0055] For the upper circle, the calculation formula for the radial velocity is V r = v l * -cos(β - θ), where V1 represents the linear velocity of the drone, V r represents the component of the linear velocity between the radiation source and the line connecting to this point, the central angle corresponding to the drone is θ, and the direction angle between the drone and the radiation source is β;

[0056] For the lower circle, the calculation formula for the radial velocity is V r = v l * -cos(β + θ), where V1 represents the linear velocity of the drone, V r represents the component of the linear velocity between the radiation source and the line connecting to this point, the central angle corresponding to the drone is θ, and the direction angle between the drone and the radiation source is β.

[0057] Further, the drone uses the measured Doppler frequency change to calculate the relative velocity between the target and the drone through an algorithm, where the calculation formula for the Doppler frequency is where f s is the signal source frequency and c is the speed of light.

[0058] Further, after determining the maximum and minimum Doppler frequency points, the drone determines the position of the radiation source by calculating the tangent slope, where the calculation formula for the tangent slope of the upper tangent circle is where κ 11 and κ 12 respectively represent the slopes of the tangents at the maximum and minimum Doppler frequency points of the upper circle, and the tangent equations of the upper circle passing through the maximum and minimum Doppler frequency points are

[0059] Further, the calculation formula for the tangent slope of the lower tangent circle is where κ 21 and κ 22 respectively represent the slopes of the tangents at the maximum and minimum Doppler frequency points of the lower circle, and the tangent equations of the upper circle passing through the maximum and minimum Doppler frequency points are

[0060] Furthermore, the midpoint of the two positions of the drone in the upper circle and the lower circle of the "8"-shaped trajectory is determined by the simultaneous tangent equations as the final position of the radiation source, where the position calculation formula is: Where (x1+x2) and (y1+y2) represent the position coordinates of the upper circle and the lower circle respectively.

[0061] Furthermore, the position coordinates determined by the upper circle and the lower circle are confirmed by the formula:

[0062] The calculation formula for the upper circle position coordinates is:

[0063] The calculation formula for the position coordinates of the lower circle is:

[0064] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A single-station positioning method for passive radar onboard an unmanned aerial vehicle based on Doppler frequency, characterized in that: The following steps are involved: S1: The UAV flies along a predetermined figure-8 trajectory, which includes an upper circle and a lower circle, and the radius of each circle is R; S2: During the flight, the drone passively receives the signal from the target radiation source and measures the Doppler frequency change; S3: The maximum and minimum Doppler frequency points are determined in the flight trajectories of the UAV in the upper circle and the lower circle, respectively; S4: Use the navigation and positioning tool of the drone to record the position coordinates of the maximum and minimum Doppler frequency points; S5: Calculate the corresponding tangent slope according to the position coordinates of the maximum and minimum Doppler frequency points; S6: Determine the two possible positions of the radiation source by solving the simultaneous tangent equations; S7: The final position of the radiation source is the midpoint of the above two possible positions.

2. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 1, characterized in that: The UAV measures and records the maximum and minimum values ​​of the radiation source signal in the flight trajectory of the upper circle and the lower circle, and the corresponding frequency points are set as 3. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 1, characterized in that: The navigation and positioning tools of the UAV include but are not limited to GPS, inertial navigation system or radio navigation system.

4. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 1, characterized in that: The flying time of the UAV on each circle of the "8" shaped trajectory is 5. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 1, characterized in that: The corresponding radial velocities are calculated when the UAV flies in the upper and lower circles of the "8"-shaped trajectory; For the upper circle, the radial velocity is calculated as V r =v l *-cos(β-θ), where V1 represents the linear velocity of the drone, V r It represents the component of the linear velocity between the radiation source and the line connecting the point. The center angle of the UAV is θ, and the direction angle between the UAV and the radiation source is β. For the lower circle, the radial velocity is calculated as V r =v l *-cos(β+θ), where V1 represents the linear velocity of the drone, V r It represents the component of the linear velocity between the radiation source and the line connecting the point. The center angle of the UAV is θ, and the direction angle between the UAV and the radiation source is β.

6. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 1, characterized in that: The UAV uses the measured Doppler frequency change to calculate the relative speed between the target and the UAV through an algorithm, where the calculation formula of the Doppler frequency is: where f s is the signal source frequency, and c is the speed of light.

7. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 2, characterized in that: After determining the maximum and minimum Doppler frequency points, the UAV determines the location of the radiation source by calculating the tangent slope, where the calculation formula for the tangent slope of the upper tangent circle is: where κ 11 and κ 12 The upper circles represent the slopes of the tangents of the maximum Doppler frequency point and the minimum Doppler frequency point, respectively. The tangent equations of the upper circles passing through the maximum and minimum Doppler frequency points are:

8. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 7, characterized in that: The calculation formula of the slope of the tangent line of the lower circle is: where κ 21 and κ 22 They represent the slopes of the tangents of the maximum Doppler frequency point and the minimum Doppler frequency point of the lower circle respectively. The tangent equation of the upper circle passing through the maximum and minimum Doppler frequency points is:

9. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 8, characterized in that: The midpoint of the two positions of the drone in the upper and lower circles of the "8"-shaped trajectory is determined by the simultaneous tangent equations as the final position of the radiation source, where the position calculation formula is: Where (x1+x2) and (y1+y2) represent the position coordinates of the upper circle and the lower circle respectively.

10. The method for positioning a single-station passive radar onboard an unmanned aerial vehicle based on Doppler frequency according to claim 9, characterized in that: The position coordinates determined by the upper circle and the lower circle are confirmed by the formula: The calculation formula for the upper circle position coordinates is: The calculation formula for the position coordinates of the lower circle is:

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